What laboratory values are typically elevated in patients undergoing dialysis?

Laboratory Values Typically Elevated in Dialysis Patients

Dialysis patients commonly experience elevations in multiple laboratory values due to impaired kidney function and the dialysis process itself, with key abnormalities including urea, creatinine, phosphate, and cardiac biomarkers.

Nitrogenous Waste Products

• Blood Urea Nitrogen (BUN): Significantly elevated in pre-dialysis samples, with levels typically decreasing but not normalizing after dialysis sessions 1
• Creatinine: Markedly elevated compared to non-dialysis patients; serves as a primary marker of kidney function 1
• Methylamine (MMA): Less efficiently cleared than urea during hemodialysis, with pre-dialysis levels approximately twice those of normal subjects 2

Electrolyte and Mineral Abnormalities

• Phosphate: Commonly elevated due to impaired excretion; requires monitoring and often phosphate binder therapy 3
• Potassium: May be elevated pre-dialysis, requiring careful monitoring as both hyper- and hypokalemia can occur 4
• Aluminum: May accumulate in dialysis patients, especially with aluminum-containing medications; levels should be <20 μg/L at baseline 3
• Magnesium: May be elevated in some patients, particularly those with reduced residual kidney function 4

Cardiac and Inflammatory Biomarkers

• Cardiac Troponin T and I: Often chronically elevated in asymptomatic dialysis patients; powerful predictors of mortality even in the absence of acute coronary syndrome 3
  • Patients with troponin T >0.1 μg/L have approximately 50% two-year mortality 3
  • Important to note that elevated troponins in dialysis patients are not spurious findings but reflect cardiac pathology 3

Bone Metabolism Markers

• Parathyroid Hormone (PTH): Often elevated due to secondary hyperparathyroidism 3
• Bone-specific Alkaline Phosphatase (bALP): May be elevated in high-turnover bone disease; values >42.1 U/L suggest high bone turnover 5
• Amino-terminal propeptide of type 1 procollagen (P1NP): May be elevated in high-turnover bone disease 5

Hepatitis Markers

• Hepatitis C Viral Load: May be present in dialysis patients; NAT testing is recommended for diagnosis as antibody testing may miss cases during the window period 3
• Alanine Aminotransferase (ALT): Monthly monitoring recommended for surveillance of HCV acquisition in hemodialysis units 3

Iron Status Indicators

• Ferritin: Often elevated due to inflammation and iron supplementation 3
• Transferrin Saturation: May be abnormal due to altered iron metabolism and supplementation 3

Clinical Implications and Monitoring

1. Pre-dialysis sampling is crucial for accurate assessment of most laboratory values, as levels fluctuate significantly during and after dialysis 6

2. Cardiac biomarkers require special interpretation:

   • Elevated troponin levels are associated with increased mortality even without acute coronary syndrome 3
   • The pattern of rise and fall is key to differentiating chronic elevation from acute coronary events 3

3. Aluminum monitoring:

   • Serum aluminum should be measured at least yearly and every 3 months in patients receiving aluminum-containing medications 3
   • DFO testing may be needed if aluminum levels are between 60-200 μg/L 3

4. Electrolyte monitoring:

   • Regular monitoring before, during, and after dialysis sessions is essential 4
   • Customized dialysate solutions may be needed based on individual electrolyte profiles 4

Common Pitfalls to Avoid

1. Misinterpreting elevated cardiac troponins as acute coronary syndrome without considering the chronic elevation pattern common in dialysis patients 3

2. Relying solely on antibody testing for HCV without NAT confirmation, which may miss cases during the window period 3

3. Inadequate monitoring of aluminum levels, particularly in patients receiving aluminum-containing medications 3

4. Failing to account for the timing of blood draws relative to dialysis sessions, which can significantly affect laboratory values 6

5. Overlooking the significance of elevated troponin T as a powerful predictor of mortality in asymptomatic dialysis patients 3